1. Field of the Invention
The present invention relates to ascorbic acid or erythorbic acid derivatives represented by the following general formula (I)a: ##STR3## wherein n represents an integer of 12 to 20, which are novel compounds not found in literature, as well as to a process for producing ascorbic acid or erythorbic acid derivatives represented by the following general formula (I)b: ##STR4## wherein n represents an integer of 4 to 20.
2. Prior Art
Having excellent fat-solubility and antioxidative property, the ascorbic acid (erythorbic acid) derivatives represented by the above-mentioned general formula (I)a and (I)b are useful in themselves alone or in combination with tocopherol or the like as an antioxidant for foodstuffs and living bodies.
Although ascorbic acid (erythorbic acid) is known as an antioxidant for foodstuffs and the like, it is not satisfactory in fat-solubility and antioxidative property. Thus, a variety of acyl-substituted derivatives of ascorbic acid have so far been synthesized tentatively. For example, Japanese Patent Kokai (Laid-Open) No. 87,655/74 disclosed a process for producing 5,6-diacyl substituted derivatives represented by the general formula (I)a or (I)b wherein n was 8 or less. However, these 5,6-diacyl substituted derivatives were yet insufficient in fat-solubility and antioxidative property.
Apart from them, acyl substituted derivatives of ascorbic (erythorbic) acid having acyl substituents on 2,6-positions, 2,5,6-positions or 2,3,5,6-positions are also known. Although an increase in the number of acyl substituent is accompanied by an increase in fat-solubility, an antioxidative property can be exhibited only when 2-position and/or 3-position are(is) not acyl-substituted. Accordingly, these polyacyl-substituted derivatives cannot be used as an antioxidant.
As the process for producing acyl-substituted derivatives of ascorbic acid or erythorbic acid, a variety of processes are known. According to the usual acylating process, monoacylation, diacylation, triacylation, tetraacylation and so on take place successively, and these acylations usually take place first at the 6-position and then at 2, 5 and 3-positions, in the mentioned order. This means that the only diacyl substituted derivative obtainable is 2,6-diacyl substituted derivative.
In Japanese Patent Kokai (Laid-Open) No. 87,655/74, there was disclosed a process for selectively producing only 5,6-diacyl substituted derivative which comprises reacting ascorbic acid with an anhydride or a halide of lower fatty acid. However, when applied to fatty acids having 4 or more carbon atoms, this process could not yield the ascorbic acid or erythorbic acid derivatives represented by the general formula (I)b.